Conversion of natural gas or gaseous hydrocarbons of methane, ethane, butane, propane and combinations thereof is useful in the commodity chemical industry. Such conversion utilizing microwave energy has been described in U.S. Pat. No. 3,663,394 and in U.S. Pat. No. 4,574,038.
More recently, U.S. Pat. No. 4,975,164 to Ravella et al. mentions microwave conversion of gaseous hydrocarbon (butane) by using "plasma initiators" that are metal (e.g. tungsten, iron, nickel, copper, etc.) with tungsten preferred or non-metal (e.g. carbon, alumina, metal oxides, metal nitrides, metal sulfides, etc.) with carbon preferred. The plasma initiator is used singly or as a spaced plurality with at least 0.25 cm spacing between plasma initiators. Ravella et al. require the presence of hydrogen to maintain activity of the plasma initiator. The mole ratio of plasma initiator (tungsten) to gaseous hydrocarbon (butane) used by Ravella et al. was from 0.0032 to 0.0048 depending upon the reaction time.
U.S. Pat. No. 4,574,038 to Wan discusses microwave conversion of a gaseous hydrocarbon (methane) by using a metal powder catalyst. Wan requires a mole ratio of metal powder catalyst to gaseous hydrocarbon (methane) of about 0.4. Wan pre-treats the metal powder with hydrogen prior to performing conversion.
U.S. Pat. No. 5,472,581 to Wan discusses microwave conversion of a gaseous hydrocarbon (methane) to a product that is primarily acetylene by using pulsed microwave energy of at least 1.5 kW (1500 W).
It is a long felt need in the art of microwave conversion of gaseous hydrocarbons to perform the conversion without hydrogen either added to the gaseous hydrocarbon or used to pre-treat the catalyst. It is a further long felt need to reduce the quantity of catalyst material necessary for the conversion.